Last reviewed: 2026-04-18 by Jake Terry, FFL07/SOT3, NRA-certified firearms instructor.
When you need terminal performance from an AR-15 chambered in 458 Socom ammo, Underwood’s 300-grain jacketed hollow point load delivers the energy and expansion to anchor medium to large game. This cartridge is purpose-built for hunters who run big-bore AR platforms — a straight-walled design that generates 2,405 foot-pounds of energy at the muzzle, nearly triple the output of 5.56 NATO, while maintaining the manual-of-arms you already know.
Performance at a Glance
Underwood loads this cartridge with a Hornady XTP bullet — a design with six symmetrical serrations that control expansion from low velocities up through magnum performance windows. At 1,900 feet per second from a 16-inch barrel, the 300-grain projectile delivers deep penetration and reliable upset on soft tissue, making it suitable for hogs, deer, and black bear at woods distances. Boxer-primed brass cases and non-corrosive propellant mean you can reload these hulls after the hunt. Underwood uses flash-suppressed powder across its entire line, preserving night vision if you take a shot in low light.
The Numbers
| Spec | Value |
|---|---|
| Caliber | 458 Socom |
| Bullet weight | 300 grains |
| Bullet type | Jacketed Hollow Point (Hornady XTP) |
| Muzzle velocity | 1,900 fps |
| Muzzle energy | 2,405 ft-lbs |
| Rounds per box | 20 |
| Case | Brass |
| Primer | Boxer |
| Corrosive | No |
| Reloadable | Yes |
| Velocity rating | Supersonic |
| Intended use | Hunting |
| Manufacturer | Underwood Ammunition (Made in USA) |
Underwood field-tests every lot with real firearms under field conditions — this ammunition is designed to perform in the rifles customers actually own, not just lab test barrels. For more big-bore AR options, browse our full 458 Socom ammo inventory.
Safe Handling & Compliance
Federal law requires purchasers to be at least 18 years old for rifle and shotgun ammunition, and at least 21 for handgun ammunition. Ammunition cannot be shipped to certain states, counties, and cities — review our ammunition shipping restrictions before ordering. Store ammunition in a cool, dry location away from heat sources and out of reach of unauthorized users.
- Always follow the four rules of firearm safety — treat every firearm as loaded, never point at anything you’re not willing to destroy, keep your finger off the trigger until ready to fire, and be certain of your target and what lies beyond it.
- Verify that your state and local jurisdiction permit ownership and purchase of this ammunition before ordering. Some jurisdictions restrict or prohibit large-bore ammunition sales.
- This ammunition contains lead. Wash hands thoroughly after handling. Pregnant women and children should avoid exposure to lead dust. See California Proposition 65 warnings.
Reviews
There are no reviews yet.